The invention concerns a device for ground compacting, having at least one vibrating roller whose casing surface is composed of a plurality of segments in a peripheral direction, at least some of which have midpoints which describe an arc having a radius of curvature that deviates from the mean radius of the roller.
Either a vibrating roller or a vibrating plate is used in known devices for ground compacting. The compacting efficiency in vibrating rollers is thereby essentially determined by the line load and the amplitude.
To obtain a high depth effect, as high an amplitude as possible of the vibrating roller is required, whereby it is usually accepted that the higher the amplitude, the higher the depth effect of the compacting.
In recent years, rollers having an increased compacting efficiency were developed, i.e. with high line loads and high amplitudes, which operate with a line load of up to 800 N/m and an amplitude of 2 mm. Rollers of this type have proved to be successful for compacting stony ground not sensitive to shearing stress, since higher fill layers can be compacted.
However, in cohesive ground and/or ground sensitive to shearing stress, the high compacting forces result in the formation of cracks. Essentially, the reason for this is that the high compacting force which acts on the ground via the round roller body, reaches the material to be compacted diagonally which generates high stresses in the surface area and results in cracks and bursts. In contrast thereto, the stresses in deeper ground fade quickly.
In view of the fact that, under these circumstances, the depth effect of ground compacting devices with vibrating rollers is limited, in certain grounds it is preferred to apply the compacting force by flat-surfaced elements, such as e.g. vibrating plates, in which the stress curve in the ground to be compacted is substantially more advantageous since no pronounced stress peaks occur in this case and, moreover, the vertically applied forces fade considerably more slowly in the deeper ground.
Although vibration plates thus compact better than rollers, compacting devices with rollers have found a broader field of application overall due to a higher power area ratio, a greater adaptability and greater climbing ability, better transportability and greater ease of control and they have often superseded plate compactors.
In order to combine the advantages of the vibrating plates with those of the roller, it was, for example, proposed in DE-A 196 48 593 to construct the vibrating roller of the ground compacting device from a plurality of individual segments in the peripheral direction, so that convex curved sections having two different curvatures are formed in the peripheral direction, alternating successively and continuously passing over into one another outward on the tire, whereby the one curvature is stronger and the other curvature is weaker than that of a cylinder defining the outer periphery of the roller. In other words, rollers of this type can also be described as flattened by segment.
It is, moreover, proposed in this publication to provide such segmented flattened rollers in pairs, namely on the front and on the rear axis of a road roller. In this way, it is to be understood that the climbing ability for the road roller is assured because, on the one hand, a tire with a segment having a weak curvature lies on the ground, while the other roller with a segment having a greater curvature simultaneously ensures the advancement of the road roller.
An advantage of this previously known roller is, in particular, that the high loads in the segments having a weak curvature are no longer inserted into the ground to be compacted as line loads with corresponding undesirable side effects, such as unintentional shearing stresses, but that these are greatly reduced since the forces are introduced into the ground via as wide a stand-up surface of the roller as possible. Carrying this idea further results in that the best results should ultimately be obtained if the individual segments of the roller are flat, i.e. its radius of curvature is endless.
Although no shearing stresses occur in the ground to be compacted in this design, the disadvantage is noted in DE-U 296 21 103 that a traction and/or climbing ability is no longer present during a vibration for tires of this type which are presumably known. Moreover, in this publication, a considerably jolting movement is considered a disadvantage for tire surfaces formed from flat sections and it is instead proposed to make the tire surface from sections which have the form of a triangle or trapezoid, wherein adjacent casing sections each have an equally long triangular or trapezoidal side in common and are arranged in such a way that a triangular side or longer trapezoidal side of the adjacent casing surface, opposite a corresponding triangular point or shorter trapezoidal side, is alternately followed by a triangular point or a shorter trapezoidal side of a preceding casing section at the front end of the tires in their peripheral direction.
However, rollers of this type have the disadvantage that their median axis for placing two adjacent casing sections each flat thereon must be tipped in each case which requires an extensive apparatus structure.
Also, in rollers of this type, it is only possible to obtain traction or climbing ability if a comparable second polygonal roller is present on a further axis of a road roller, said second polygonal roller ensuring the forward movement with an edge while a flat section ensures the desired ground compacting on the first-mentioned tire.
In the two previously known road rollers, a good synchronization must be assured for the rotation of the rollers on both axes, as can be seen in the above, said synchronization ensuring the described phase-displaced rotation of the two rollers on the front and rear axes on a continuous basis.
Thus, the object of the present invention is to further develop a roller, as described above, in such a way that it has as good an automatic synchronization as possible. Moreover, a possibility should be given to make it possible to omit the extensive synchronization of the front and rear axes when using two rollers on a road roller.
According to the invention, this object is solved by a corresponding roller that has several adjacent sections in an axial direction consisting of segments abutting one another in a peripheral direction and which have abutting edges displaced vis-à-vis one another in the peripheral direction.
The advantage of these rollers lies therein that their xe2x80x9crolling behaviorxe2x80x9d is improved considerably. At the same time, the compacting and the advancement and/or climbing ability can be realized with only one roller. Moreover, the effect of the sections arranged so as to be displaced vis-à-vis one another in the peripheral direction is to reinforce the individual segments, as a result of which an even more improved transmission of the vibration forces to the ground material to be compacted is obtained.
Preferably, corresponding rollers have between 2-7 corresponding adjacent sections.
To obtain a compacting that meets the requirements, it is proposed to provide the vibrating roller with a directional vibrator which can, if necessary, be adapted to the ground in the direction of and/or the amplitude of its vibrating force.
In this connection, it is furthermore proposed to turn the roller intermittently via a stepped gear, whereby this stepped gear can, for example, be coupled with a device for detecting a vibration speed of the directional vibrator. It is thus ensured that a given vibration speed is applied to each ground section on which the roller comes to rest with a flattened segment and to thus ensure a desired compacting result.
It is also possible to couple the stepped gear with a device to move the vibrating roller, said device directly determining the ground compacting by means of various parameters and, when a set value is reached, to then actuate the stepped gear to shift it to a next segment.
Finally, with a compacting device of this type which moves forward intermittently, it is ensured that the contact time of the flattened vibrating segments is sufficient in each case for the desired compacting result.
Surprisingly, it is also possible to ascertain very good compacting results if the individual segments have a slightly concave slope directed to the roller axis.
Furthermore, it was found that the climbing ability was even more improved when the abutting edges of the flattened segments were provided with serrated slats protruding in a radial direction which can, moreover, be made of a harder material and thus reduce wear which is greater at this point.
To eliminate the impressions which are caused by the polygonal points in the ground to be compacted and which can be seen at the abutting edges between individual segments of a section in the roller cross section, it is, moreover, proposed to equip the compacting devices with a smooth roller surface with which the undesirable surface structure can be subsequently compacted and smoothed.
In addition, it is also proposed to provide a roller with circular cylindrical sections. In particular, this enables a very quiet mode of travel, especially on approaching and departing paths that run on Roads. Preferably, these circular sections are here provided in the vicinity of the axial ends of the roller in order to increase the stability of the compacting device.